One common formula suggests that a 2-year-old cat is comparable to a 24-year-old human in terms of maturity. For each subsequent calendar year, another 4 years is added to the cat's age. By this formula, a 3-year-old cat is 28 in cat years, and a 7-year-old cat is 44.
Cats mature quickly in the first few years of life, reaching full-growth and maturity before they are two years old. The maximum age for most cats is about 20 years, which is roughly equivalent to 96 years in human terms, but it isn't uncommon for cats to live past 20. There are documented cases of cats living past 30, though this is very unusual. On average, keeping a cat indoors typically doubles its lifespan.